JPWO2005041277A1 - Illumination optical device and projection exposure apparatus - Google Patents

Abstract

An illumination optical device and a projection exposure apparatus capable of reducing a light amount loss when illuminating a mask with illumination light having a predetermined polarization state. It has an illumination optical system (ILS) that illuminates the reticle (R) with illumination light (IL), and a projection optical system (PL) that projects an image of the pattern of the reticle (R) onto the wafer (W). In the illumination optical system (ILS), the illumination light (IL) emitted from the exposure light source (1) in a linearly polarized state passes through the first and second birefringent members (12, 13) having different fast axis directions. After passing through and converted into a polarization state that becomes substantially linearly polarized light in a circumferential direction around the optical axis in a substantially specific ring-shaped region, the reticle (R) is passed through a fly-eye lens (14) and the like. Is illuminated under the conditions of ring illumination.

Description

  The present invention relates to an illumination technique and an exposure technique used in a lithography process for manufacturing various devices such as a semiconductor integrated circuit (LSI or the like), an image sensor, or a liquid crystal display, and more specifically, a mask pattern having a predetermined polarization. The present invention relates to an illumination technique and an exposure technique for illuminating with state light. The present invention also relates to a device manufacturing technique using the exposure technique.

  When forming a fine pattern of an electronic device such as a semiconductor integrated circuit or a liquid crystal display, a pattern of a reticle (or photomask, etc.) as a mask, which is drawn by proportionally enlarging the pattern to be formed by about 4 to 5 times, is projected. A method is used in which a wafer (or a glass plate or the like) as a substrate to be exposed (photoconductor) is reduced and exposed and transferred via an optical system. In the exposure transfer, a static exposure type projection exposure apparatus such as a stepper and a scanning exposure type projection exposure apparatus such as a scanning stepper are used. The resolution of the projection optical system is proportional to the exposure wavelength divided by the numerical aperture (NA) of the projection optical system. The numerical aperture (NA) of the projection optical system is obtained by multiplying the sine (sin) of the maximum incident angle of the illumination light for exposure on the wafer by the refractive index of the medium through which the light flux passes.

Therefore, the exposure wavelength of the projection exposure apparatus has been shortened to cope with the miniaturization of semiconductor integrated circuits and the like. At present, the exposure wavelength is mainly 248 nm of the KrF excimer laser, but 193 nm of the shorter wavelength ArF excimer laser is entering the stage of practical application. Further, there has been proposed a projection exposure apparatus using an exposure light source in the so-called vacuum ultraviolet region, such as an F ₂ laser having a wavelength of 157 nm and a Ar ₂ laser having a wavelength of 126 nm, which have shorter wavelengths. Further, not only shortening the wavelength but also increasing the resolution by increasing the numerical aperture of the projection optical system (increasing the NA), so development has been made to further increase the NA of the projection optical system. The NA of the current state-of-the-art projection optical system is about 0.8.

On the other hand, even if a projection optical system having the same exposure wavelength and the same NA is used, as a technique for improving the resolution of a transferred pattern, a method using a so-called phase shift reticle or an incident angle distribution of illumination light on a reticle is predetermined. So-called super-resolution techniques such as annular illumination, two-pole illumination, and four-pole illumination that are controlled by distribution have also been put to practical use.
Among them, the annular illumination limits the incident angle range of the illumination light to the reticle to a predetermined angle, that is, the illumination light distribution on the pupil plane of the illumination optical system is centered on the optical axis of the illumination optical system. By limiting the area to a predetermined ring zone area, it is effective in improving the resolution and the depth of focus (see, for example, JP-A-61-91662). On the other hand, the two-pole illumination and the four-pole illumination correspond not only to the incident angle range but also to the direction of the illumination light incident direction when the pattern on the reticle has a specific directionality. By limiting the direction, the resolution and the depth of focus can be significantly improved (for example, Japanese Patent Application Laid-Open No. 4-101148 or US Patent No. 6233041 equivalent thereto, Japanese Patent Application Laid-Open No. 4-225357 or equivalent). U.S. Pat. No. 6,211,944).

  An attempt to optimize the polarization state of the illumination light with respect to the pattern direction on the reticle to improve the resolution and the depth of focus has also been proposed. In this method, the illumination light is changed to a linearly polarized light having a polarization direction (electric field direction) in a direction orthogonal to the periodic direction of the pattern, that is, in a direction parallel to the longitudinal direction of the pattern, so that the contrast of a transferred image is improved. It is improved (see, for example, Patent Document 1 and Non-Patent Document 1).

Also, in annular illumination, the polarization direction of the illumination light should be matched with the circumferential direction in the annular area where the illumination light is distributed on the pupil plane of the illumination optical system to improve the resolution and contrast of the projected image. Attempts have been proposed.
JP-A-5-109601 Thimothy A. Brunner, et al.: "High NA Lithographic imaging at Brewster's ange1", SPIE (USA) Vo1.4691, pp.1-24 (2002)

In the prior art as described above, in the case of performing annular illumination, in the pupil plane of the illumination optical system, if an attempt is made to make the polarization state of the illumination light into linearly polarized light that substantially coincides with the circumferential direction of the annular area, There is a problem that the loss of light amount increases and the illumination efficiency decreases.
More specifically, the illumination light emitted from the narrow-band KrF excimer laser light source, which is the mainstream in recent years, is uniform linearly polarized light. If this is guided to the reticle while maintaining the same polarization state, the reticle is illuminated with uniform linearly polarized light, so a straight line that coincides with the circumferential direction of the annular zone of the pupil plane of the illumination optical system as described above. It goes without saying that polarized light cannot be realized.

  Therefore, in order to realize the above-mentioned polarization state, after linearly polarized light emitted from a light source is once converted into randomly polarized light, a polarization selection element such as a polarization filter or a polarization beam splitter is provided in each part of the annular zone. It was necessary to adopt a method of selecting a desired polarization component from the illumination light composed of randomly polarized light by using the above. In this method, only the energy contained in the predetermined linearly polarized light component of the energy of the randomly polarized illumination light, that is, only about half the energy can be used as the illumination light to the reticle, so the loss of the illumination light amount is large, As a result, there is a problem that the exposure power to the wafer is large and the processing capability (throughput) of the exposure apparatus is reduced.

  Similarly, when using multiple-pole illumination such as two-pole illumination or four-pole illumination, the polarization state of the illumination light in the two-pole or four-pole region on the pupil plane of the illumination optical system should be set to a predetermined state. Then, there is a problem that the lighting efficiency is reduced.

The present invention has been made in view of the above problems, and it is a first object of the present invention to provide an exposure technique capable of reducing a light amount loss when a mask such as a reticle is illuminated with illumination light having a predetermined polarization state. And
Further, according to the present invention, when setting the polarization state of the illumination light in a region such as an annular zone, two poles, or four poles on the pupil plane of the illumination optical system to a predetermined state, it is possible to reduce the reduction of the illumination light amount, and as a result, A second object of the present invention is to provide an illumination technique and an exposure technique that can improve the resolution and the like without substantially lowering the processing capacity.
Another object of the present invention is to provide a device manufacturing technique capable of manufacturing a high-performance device with high processing capacity by using the above-mentioned exposure technique.

The reference numerals with parentheses attached to the respective elements of the present invention below correspond to the configurations of the embodiments of the present invention described later. However, each symbol is merely an example of the element, and each element is not limited to the configuration of the embodiment.
A first projection exposure apparatus according to the present invention includes an illumination optical system (ILS) for irradiating a first object (R) with illumination light from a light source (1) and a pattern image on the first object for a second object. Projection exposure system (25) for projecting onto (W), the light source producing the illumination light in a substantially single polarization state, the illumination optical system comprising: It has a plurality of birefringent members (12, 13) arranged along the traveling direction of the illumination light, and the direction of the fast axis of at least one birefringent member of the plurality of birefringent members is different from that of the other birefringent members. Of the illumination light, which is different from the direction of the fast axis of the birefringent member, the specific illumination light that irradiates the first object in the specific incident angle range has a polarization state of S polarization as a main component. It is to be light.

  The first illumination optical device according to the present invention is an illumination optical device that illuminates the first object (R) with the illumination light from the light source (1), and is arranged along the traveling direction of the illumination light. It has a plurality of birefringent members (12, 13), and the direction of the fast axis of at least one of the plurality of birefringent members is different from the direction of the fast axis of other birefringent members. Of the illumination light having a substantially single polarization state that is supplied from the light source, the specific illumination light that is emitted to the first object in the specific incident angle range is mainly S-polarized light. The light having a polarized state is set.

  According to the present invention, for example, by setting the thickness distribution of each of the plurality of birefringent members to a predetermined distribution, the illumination light emitted from the light source passes through the plurality of birefringent members. The subsequent polarization state can be mainly composed of, for example, a ring-shaped region centered on the optical axis and polarized in the circumferential direction about the optical axis. Therefore, by arranging the exit surfaces of the plurality of birefringent members at a position close to the pupil plane of the illumination optical system, for example, the illumination light (specific illumination light) that has passed through the ring-shaped region has a light amount loss. The first object is illuminated in a predetermined polarization state having S-polarized light as a main component in a state where there is almost no light.

  In this case, you may have the light beam limitation member (9a, 9b) which limits the illumination light with which the 1st object is irradiated to the specific illumination light. As a result, the first object is illuminated under substantially annular illumination conditions. With this annular illumination, by making the illumination light on the first object almost S-polarized, the projected image of the line-and-space pattern arranged on the first object at a fine pitch in an arbitrary direction is obtained. Since the image is mainly formed by the illumination light whose polarization direction is parallel to the longitudinal direction of the line pattern, the image forming characteristics such as contrast, resolution and depth of focus are improved.

Further, the light flux limiting member may further limit the incident direction of the illumination light with which the first object is irradiated to a plurality of specific substantially discrete directions. As a result, since illumination is performed by dipole illumination, quadrupole illumination, or the like, the imaging characteristics of the line-and-space pattern arranged at a fine pitch in a predetermined direction are improved.
Next, the second projection exposure apparatus according to the present invention provides an illumination optical system (ILS) for illuminating the first object (R) with illumination light from the light source (1) and an image of the pattern on the first object. A projection exposure apparatus having a projection optical system (25) for projecting onto a second object (W), the light source of which produces its illumination light in a substantially single polarization state, and the illumination optical system. Has a plurality of birefringent members (12, 13) arranged along the traveling direction of the illumination light, and the direction of the fast axis of at least one birefringent member among the plurality of birefringent members is , A predetermined ring zone centered on the optical axis of the illumination optical system in the plane of the pupil plane in the illumination optical system or in the vicinity thereof, which is different from the direction of the fast axis of the other birefringent member. The illumination light passing through at least a part of the specific ring zone region (36) is a polarization state whose main component is linearly polarized light whose polarization direction is the circumferential direction of the specific ring zone region. Is.

  According to the present invention, for example, by setting the thickness distributions of the plurality of birefringent members to predetermined distributions, the illumination light emitted from the light source passes through the specific annular zone region. The polarization state of at least a part of the illumination light is in a state where there is almost no loss of light amount and the main component is a linearly polarized light whose polarization direction is the circumferential direction of the specific ring zone region (predetermined polarization state).

  In this case, a light flux limiting member (9a, 9b) may be provided to limit the illumination light applied to the first object to a light flux substantially distributed in the specific ring zone area. Further, the light flux limiting member may further limit the light flux into a plurality of substantially discrete areas within the specific ring zone area. In these cases, annular illumination, two-pole illumination, four-pole illumination, or the like can be realized with almost no reduction in the amount of illumination light.

Further, the light flux limiting member includes, for example, a diffractive optical element arranged between the light source (1) and the plurality of birefringent members (12, 13). By using the diffractive optical element, the light amount loss can be further reduced.
Further, as an example, at least one member of the plurality of birefringent members has a phase difference between the linearly polarized light component parallel to the fast axis and the linearly polarized light component parallel to the slow axis in the transmitted light. It is a non-uniform wave plate (12, 13) in which a certain phase difference between polarized lights changes non-linearly with respect to the position of the member. This makes it possible to control the polarization state of the illumination light after passing through the plurality of birefringent members to a predetermined state with high accuracy.

In this case, the non-uniform wave plate has a phase difference between polarizations having two-fold rotational symmetry about the optical axis of the illumination optical system with respect to the specific illumination light or the illumination light distributed in the specific ring zone region. May include a first non-uniform wave plate (12) that provides
Further, the nonuniform wave plate has a phase difference between polarizations having one-time rotational symmetry about the optical axis of the illumination optical system, with respect to the specific illumination light or the illumination light distributed in the specific ring zone region. It may further include a second non-uniform wave plate (13) for providing.

In addition, as an example, the first and second non-uniform wave plates are such that the directions of the fast axes thereof are deviated from each other by 45° about the optical axis of the illumination optical system as a rotation center. This facilitates control of the polarization state of the illumination light after passing through the two nonuniform wave plates.
Further, it may further include an optical integrator (14) arranged between the plurality of birefringent members and the first object. This improves the uniformity of the illuminance distribution on the first object.

  Further, it may further include a zoom optical system arranged between the plurality of birefringent members and the optical integrator, a conical prism group (41, 42) with variable spacing, or a polyhedral prism group. According to the pitch of the pattern on the first object, the size and position of the specific ring zone area (or the ring zone area or substantially discrete partial areas therein) are determined by using the zoom optical system or the like. By controlling, it is possible to improve the imaging characteristics when exposing patterns of various pitches.

The optical integrator is, for example, a fly-eye lens.
A polarization control mechanism (4) arranged between the light source and the plurality of birefringent members and converting the polarization state of the illumination light from the light source may be included. Thereby, the polarization state of the illumination light from the light source can be converted into a polarization state suitable for the plurality of birefringent members without loss of light quantity.

In addition, a rotation mechanism that allows some or all of the plurality of birefringent members to rotate about the optical axis of the illumination optical system may be provided. Thereby, the illumination light from the light source can be supplied to the birefringent member in a polarization state suitable for the birefringent member.
A plurality of sets of the plurality of birefringent members may be provided, and a plurality of sets of the plurality of birefringent members may be exchangeably arranged in the illumination optical system. This makes it possible to deal with various patterns to be transferred.

Next, the third projection exposure apparatus according to the present invention provides an illumination optical system (ILS) for illuminating the first object (R) with the illumination light from the light source (1) and an image of the pattern on the first object. A projection exposure apparatus having a projection optical system (25) for projecting onto a second object (W), the light source of which produces its illumination light in a substantially single polarization state, and the illumination optical system. Has a diffractive optical element (9a, 9b) and a birefringent member (12, 13) which are sequentially arranged along the traveling direction of the illumination light.
A second illumination optical device according to the present invention is an illumination optical device that illuminates the first object with illumination light from a light source, and includes diffractive optical elements that are sequentially arranged along the traveling direction of the illumination light. And a birefringent member.

According to the present invention, by using the birefringent member, it is possible to efficiently illuminate the first object in a predetermined polarization state having S-polarized light as a main component, for example. Furthermore, by using the diffractive optical element and limiting the light amount distribution of the illumination light incident on the birefringent member to a ring shape or the like, the light amount loss can be made extremely small.
In the present invention, as an example, the diffractive optical element substantially limits the illumination light emitted to the first object to the specific illumination light emitted to the first object within a specific incident angle range, and The birefringent member uses the specific illumination light as light having a polarization state whose main component is S-polarized light.

Further, the diffractive optical element may further limit the incident direction of the illumination light with which the first object is irradiated to a plurality of specific substantially discrete directions.
Further, the diffractive optical element distributes the illumination light in a specific annular zone area which is a predetermined annular zone area centered on the optical axis of the illumination optical system in the pupil plane of the illumination optical system. The birefringent member may substantially limit the luminous flux, and the birefringent member may have the luminous flux in a polarization state whose main component is linearly polarized light having a deflection direction in the circumferential direction.
Further, the diffractive optical element may further limit the light beam to a plurality of substantially discrete regions within the specific ring zone region.

Next, the exposure method according to the present invention uses the projection exposure apparatus of the present invention to expose the photoconductor (W) as the second object with the image of the pattern of the mask (R) as the first object. Is. According to the present invention, the first object can be illuminated by annular illumination, two-pole illumination, four-pole illumination, or the like, and the polarization state of the illumination light incident on the first object can be mainly S-polarized. it can. Therefore, the pattern formed on the mask at a fine pitch in a predetermined direction can be transferred with good image forming characteristics with almost no loss of light amount.
Further, the device manufacturing method according to the present invention is a device manufacturing method including a lithography step, and in the lithography step, the pattern is transferred to the photoreceptor by using the exposure method of the present invention. According to the present invention, it is possible to transfer a pattern with high processing capability and high imaging characteristics.

According to the present invention, the polarization state of illumination light is controlled using a plurality of birefringent members, or illumination light is used using a diffractive optical element and a birefringent member that are sequentially arranged along the traveling direction of the illumination light. Since the polarization state is controlled, it is possible to reduce the light amount loss when the first object (mask) is illuminated with the illumination light having the predetermined polarization state.
Further, by further using the light flux limiting member, when illuminating the first object with the annular illumination, the two-pole illumination, the four-pole illumination, or the like, at least one of the specific annular regions is reduced without substantially reducing the illumination light amount. The polarization state of the illumination light passing through the partial area can be set to a state where the main component is linearly polarized light parallel to the circumferential direction of the specific ring zone area.

  In this case, the imaging characteristics when exposing a pattern in which line patterns having a longitudinal direction along the direction of the linearly polarized light on the first object are arranged at a fine pitch are improved. Therefore, it is possible to provide an illumination optical device, a projection exposure apparatus, and an exposure method that can improve the imaging characteristics without lowering the processing capacity (throughput).

FIG. 1 is a partially cutaway view showing a schematic configuration of a projection exposure apparatus according to an exemplary embodiment of the present invention. 2A is a view of the birefringent member 12 in FIG. 1 viewed in the +Y direction, and FIG. 2B is a cross-sectional view taken along the line AA′ of FIG. 3A is a view of the birefringent member 13 in FIG. 1 viewed in the +Y direction, and FIG. 3B is a cross-sectional view taken along the line BB′ of FIG. FIG. 4A is a diagram showing an example of the relationship between the polarization phase difference ΔP1 and the position X in the first birefringent member 12, and FIG. 4B is the polarization phase difference ΔP2 in the second birefringent member 13. And FIG. 4C is a diagram showing an example of the polarization state of the illumination light emitted from the second birefringent member 13, and FIG. FIG. 5 is a diagram showing an example of the polarization state of the illumination light emitted from the first birefringent member 12. FIG. 6A is a diagram showing another example of the relationship between the polarization phase difference ΔP1 and the position X in the first birefringent member 12, and FIG. 6B is the polarization position in the second birefringent member 13. FIG. 6C is a diagram showing another example of the relationship between the phase difference ΔP2 and the position XZ, and FIG. 6C is a diagram showing another example of the polarization state of the illumination light emitted from the second birefringent member 13. FIG. 7A is a plan view showing an example of a fine periodic pattern PX formed on the reticle R of FIG. 1, and FIG. 7B is a projection when the pattern of FIG. 7A is illuminated under a predetermined condition. FIG. 7C is a diagram showing a distribution of diffracted light formed in the pupil plane 26 of the optical system, and FIG. 7C is a diagram showing conditions of annular illumination for illuminating the pattern PX of FIG. 7A. FIG. 8A is a perspective view which simply shows the relationship between the pupil plane 15 of the illumination optical system ILS of FIG. 1 and the reticle R, and FIG. 8B shows a part of FIG. 8A in the +Y direction. 8C is a view of a part of FIG. 8A viewed in the -X direction. FIG. 9 shows a plurality of conical prisms that can be arranged between the birefringent members 12 and 13 and the fly-eye lens 14 of FIG. 1 in order to make the radius of a specific ring zone variable in an example of an embodiment of the present invention. FIG. FIG. 10 is a diagram showing an example of a polarization control optical system that can be arranged at the position of the polarization control member 4 in FIG. FIG. 11 is a diagram showing an example of a lithography process for manufacturing a semiconductor device using the projection exposure apparatus of the embodiment of the present invention.

Explanation of symbols

  R... Reticle, W... Wafer, ILS... Illumination optical system, AX2... Illumination system optical axis, nf... Fast axis, ns... Slow axis, 1... Exposure light source, 4... Polarization control member, 9a, 9b... Diffractive optics Element, 12... First birefringent member, 13... Second birefringent member, 14... Fly-eye lens, 25... Projection optical system, 36... Specific ring zone region, 41, 42... Conical prism

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to the drawings. In this example, the present invention is applied when exposure is performed by a scanning exposure type projection exposure apparatus (scanning stepper) of a step-and-scan system.
FIG. 1 is a partially cutaway view showing a schematic configuration of the projection exposure apparatus of this example. In FIG. 1, the projection exposure apparatus of this example includes an illumination optical system ILS and a projection optical system 25. ing. The former illumination optical system ILS includes a plurality of optical members arranged along the optical axes (illumination system optical axes) AX1, AX2, AX3 from the exposure light source 1 (light source) to the condenser lens 20 (details will be described later). The illumination light (exposure light) IL for exposure as the exposure beam from the exposure light source 1 illuminates the illumination field of the pattern surface (reticle surface) of the reticle R as a mask with a uniform illuminance distribution. Under the illumination light, the latter projection optical system 25 reduces an image obtained by reducing the pattern in the illumination field of the reticle R at a projection magnification M (M is a reduction magnification such as 1/4 and 1/5). The image is projected onto an exposure area on one shot area on the wafer W coated with a photoresist as a substrate to be exposed or a photoconductor. The reticle R and the wafer W can be regarded as a first object and a second object, respectively. The wafer W is a disk-shaped substrate having a diameter of about 200 to 300 mm, such as a semiconductor (silicon or the like) or SOI (silicon on insulator). The projection optical system 25 of this example is, for example, a dioptric system, but a catadioptric system or the like can also be used.

  Hereinafter, in FIG. 1, with respect to the projection optical system 25, the reticle R, and the wafer W, the Z axis is taken parallel to the optical axis AX4 of the projection optical system 25, and scanning exposure is performed within a plane (XY plane) perpendicular to the Z axis. In the explanation, the Y axis is taken along the scanning direction (direction parallel to the paper surface of FIG. 1) of the reticle R and the wafer W at the time, and the X axis is taken along the non-scanning direction (direction perpendicular to the paper surface of FIG. 1). To do. In this case, the illumination field of the reticle R is an elongated area in the X direction which is the non-scanning direction, and the exposure area on the wafer W is an elongated area conjugate with the illumination field. Further, the optical axis AX4 of the projection optical system 25 matches the illumination system optical axis AX3 on the reticle R.

  First, the reticle R on which the pattern to be exposed and transferred is formed is adsorbed and held on the reticle stage 21, and the reticle stage 21 moves on the reticle base 22 in the Y direction at a constant speed, and at the same time, to correct a synchronization error X Direction, the Y direction, and the rotational direction around the Z axis are finely moved to scan the reticle R. The X-direction and Y-direction positions and the rotation angle of the reticle stage 21 are measured by a movable mirror 23 and a laser interferometer 24 provided thereon. Based on this measurement value and the control information from the main control system 34, the reticle stage drive system 32 controls the position and speed of the reticle stage 21 via a drive mechanism (not shown) such as a linear motor. A reticle alignment microscope (not shown) for reticle alignment is arranged above the peripheral portion of the reticle R.

  On the other hand, the wafer W is suction-held on a wafer stage 27 via a wafer holder (not shown), and the wafer stage 27 can move on the wafer base 30 at a constant speed in the Y direction, and can be stepped in the X direction and the Y direction. It is placed so that it can be moved. The wafer stage 27 also incorporates a Z leveling mechanism for aligning the surface of the wafer W with the image plane of the projection optical system 25 based on the measurement value of an autofocus sensor (not shown). The position and rotation angle of the wafer stage 27 in the X and Y directions are measured by a movable mirror 28 and a laser interferometer 29 provided on the wafer stage 27. Based on this measured value and the control information from the main control system 34, the wafer stage drive system 33 controls the position and speed of the wafer stage 27 via a drive mechanism (not shown) such as a linear motor. In addition, an alignment sensor 31 of, for example, an FIA (Fie1d Image A1ignment) type that is an off-axis type that detects the position of the alignment mark on the wafer W for wafer alignment is disposed near the projection optical system 25. ing.

  Prior to the exposure by the projection exposure apparatus of this example, the reticle R is aligned by the reticle alignment microscope, and the position of the alignment mark formed on the wafer W together with the circuit pattern in the previous exposure process is measured by the alignment sensor. The wafer W is aligned by the detection at 31. After that, in a state where the illumination field IL on the reticle R is irradiated with the illumination light IL, the reticle stage 21 and the wafer stage 27 are driven to synchronously scan the reticle R and one shot area on the wafer W in the Y direction. Then, the operation of stopping the emission of the illumination light IL and driving the wafer stage 27 to move the wafer W stepwise in the X and Y directions is repeated. The ratio of the scanning speeds of the reticle stage 21 and the wafer stage 27 during the synchronous scanning is such that the projection magnification of the projection optical system 25 is maintained in order to maintain the image formation relationship between the reticle R and the wafer W via the projection optical system 25. Equal to M. By these operations, the pattern image of the reticle R is exposed and transferred to the entire shot area on the wafer W by the step-and-scan method.

Next, the configuration of the illumination optical system ILS of this example will be described in detail. In FIG. 1, an ArF (argon fluorine) excimer laser (wavelength 193 nm) is used as the exposure light source 1 of this example. As the exposure light source 1, other laser light sources such as KrF (krypton fluorine) excimer laser (wavelength 248 nm), F ₂ (fluorine molecule) laser (wavelength 157 nm), or Kr ₂ (krypton molecule) laser (wavelength 146 nm). Can also be used. These laser light sources (including the exposure light source 1) are narrow band lasers or wavelength-selected lasers, and the illumination light IL emitted from the exposure light source 1 is linearly polarized by the narrow band or wavelength selections. The polarized state is mainly composed of. In the following, in FIG. 1, the illumination light IL immediately after being emitted from the exposure light source 1 will be described as mainly composed of linearly polarized light whose polarization direction (electric field direction) matches the X direction in FIG.

  The illumination light IL emitted from the exposure light source 1 is incident on a polarization control member 4 (details will be described later) as a polarization control mechanism via the relay lenses 2 and 3 along the illumination system optical axis AX1. The illumination light IL emitted from the polarization control member 4 passes through a zoom optical system (5, 6) including a combination of a concave lens 5 and a convex lens 6, is reflected by a mirror 7 for bending an optical path, and is directed to an illumination system optical axis AX2. It is incident on a diffractive optical element (DOE) 9a along with. The diffractive optical element 9a is composed of a phase type diffraction grating, and the incident illumination light IL is diffracted in a predetermined direction and proceeds.

  As will be described later, the diffraction angle and the direction of each diffracted light from the diffractive optical element 9a as the light flux limiting member are set to the position of the illumination light IL on the pupil plane 15 of the illumination optical system ILS or the reticle R of the illumination light IL. Angle of incidence and direction. A plurality of diffractive optical elements 9a and another diffractive optical element 9b having a different diffractive action are arranged on the turret-shaped member 8. Then, for example, under the control of the main control system 34, the member 8 is driven by the exchange mechanism 10 to load the diffractive optical element 9a or the like at an arbitrary position on the member 8 at a position on the illumination system optical axis AX2. Then, according to the pattern of the reticle R, the incident angle range and direction of the illumination light on the reticle R (or the position of the illumination light on the pupil plane 15) can be set to a desired range. Further, the incident angle range can be supplementarily finely adjusted by moving the concave lens 5 and the convex lens 6 constituting the zoom optical system (5, 6) in the direction of the illumination system optical axis AX1. it can.

  The illumination light (diffracted light) IL emitted from the diffractive optical element 9a passes through the relay lens 11 along the illumination system optical axis AX2, and then the first birefringent member 12 and the second birefringent member 12 serving as the plurality of birefringent members of the present invention. The light is sequentially incident on the birefringent member 13. Details of these birefringent members will be described later. In the present embodiment, a fly-eye lens 14 which is an optical integrator (illuminance uniformizing member) is arranged after the birefringent member 13. The illumination light IL emitted from the fly-eye lens 14 passes through the relay lens 16, the field stop 17, and the condenser lens 18 to reach the mirror 19 for bending the optical path, and the illumination light IL reflected here is the illumination system optical axis AX3. The reticle R is illuminated via the condenser lens 20 along the line. The pattern on the reticle R illuminated in this way is projected and transferred onto the wafer W by the projection optical system 25 as described above.

If necessary, the field stop 17 may be of a scanning type, and scanning may be performed in synchronization with the scanning of the reticle stage 21 and the wafer stage 27. In this case, the field diaphragm may be divided into a fixed field diaphragm and a movable field diaphragm.
In this structure, the exit side surface of the fly-eye lens 14 is located near the pupil plane 15 of the illumination optical system ILS. The pupil plane 15 has a pattern of the reticle R via the optical members (relay lens 16, field stop 17, condenser lenses 18 and 20, and mirror 19) in the illumination optical system ILS from the pupil plane 15 to the reticle R. It acts as an optical Fourier transform surface for the surface (reticle surface). That is, the illumination light emitted from one point on the pupil plane 15 becomes a substantially parallel light flux and illuminates the reticle R at a predetermined incident angle and incident direction. The incident angle and the incident direction are determined according to the position of the light flux on the pupil plane 15.

  The optical path bending mirrors 7 and 19 are not essential in terms of optical performance, but when the illumination optical system ILS is arranged in a straight line, the overall height (height in the Z direction) of the exposure apparatus increases, It is arranged in a proper place in the illumination optical system ILS for the purpose of space saving. The illumination system optical axis AX1 coincides with the illumination system optical axis AX2 due to the reflection of the mirror 7, and the illumination system optical axis AX2 coincides with the illumination system optical axis AX3 due to the reflection of the mirror 19.

Hereinafter, a first embodiment of the first and second birefringent members 12 and 13 in FIG. 1 will be described with reference to FIGS.
The first birefringent member 12 is a disk-shaped member made of a birefringent material such as a uniaxial crystal, and its optical axis is in the in-plane direction (direction parallel to the plane perpendicular to the illumination system optical axis AX2). is there. The size (diameter) of the first birefringent member 12 in the in-plane direction is larger than the luminous flux diameter of the illumination light IL at the position where the birefringent member 12 is arranged.
2A is a view of the birefringent member 12 of FIG. 1 seen in the +Y direction along the illumination system optical axis AX2, and as shown in FIG. The fast axis nf, which is the axial direction that minimizes the refractive index for linearly polarized light having different polarization directions, is rotated by 45° from each coordinate axis (X axis and Z axis) at the XZ coordinate, which is the same coordinate axis as in FIG. Is facing the same direction. In addition, the slow axis ns, which is the axial direction that maximizes the refractive index for linearly polarized light having a polarization direction parallel to this, is of course orthogonal to the fast axis nf, and also the X axis and the Z axis. It is turned from both sides by 45°.

  The thickness of the first birefringent member 12 is not uniform in the plane parallel to the paper surface of FIG. 2A, but changes according to the X coordinate (position in the X direction). 2B is a cross-sectional view of the birefringent member 12 taken along the line AA′ of FIG. 2A. As shown in FIG. 2B, the birefringent member 12 is centered in the X direction (illumination system). The shape is thin on the optical axis and thick on the periphery. On the other hand, the thickness of the first birefringent member 12 is uniform in the Z direction of FIG. 2(A), and the birefringent member 12 is shaped like a negative cylinder lens as a whole.

  A light beam that has passed through such a birefringent member is generally linearly polarized light whose polarization direction (that is, “the vibration direction of the electric field of light”, the same applies hereinafter) matches the direction of the fast axis nf. An optical path difference (phase difference between polarizations) occurs between the component and the linearly polarized light component that coincides with the direction of the slow axis ns. The birefringent member has a low refractive index with respect to linearly polarized light parallel to the fast axis nf, and therefore the traveling speed of the same polarized light is fast, while the birefringent light has birefringence with respect to linearly polarized light parallel to the slow axis nS. Since the refractive index of the refracting member is high and the traveling speed of the same polarized light is slow, an optical path difference (polarized light phase difference) occurs between the polarized lights. Therefore, the first birefringent member 12 functions as a first non-uniform wave plate in which the phase difference between the polarized lights given to the transmitted light differs depending on the place.

  By optimizing the thickness of the first birefringent member 12, if the optical path difference caused by the birefringent member 12 is set to an integral multiple of the wavelength, the phases of the two light beams cannot be substantially distinguished, and thus the phases of the two light beams cannot be substantially distinguished. It is possible to form a state in which there is no optical path difference. In this example, the thickness T1 of the central portion of the birefringent member 12 is set to such a thickness. In the following, as shown in FIG. 2B, the origin of the X axis (X=0) is the center of the birefringent member 12 (illumination system optical axis).

  On the other hand, at a position separated by ±1 in the X direction with respect to the center of the first birefringent member 12 (1 is a reference length and is inside the outer diameter of the first birefringent member 12), the polarization between The shape of the birefringent member 12 is set so that a phase difference of 0.5 (unit: wavelength of illumination light) occurs. As such a shape, in this example, the thickness TA of the birefringent member 12 is set to the thickness represented by the following function at the position X in the X direction.

TA=T1+α×(1.7×X ⁴ −0.7×X ² ) (1)
Here, α is a proportional coefficient, and the value of α differs depending on the difference in the refractive index between the fast axis and the slow axis of the birefringent material used, as in the case of the thickness T1 of the central portion.
If quartz, which is a uniaxial crystal, is used as the birefringent material that forms the first birefringent member 12, the refractive index of the quartz is 1.6638 for the ordinary ray and the extraordinary ray for the ArF excimer laser light with a wavelength of 193 nm. Has a refractive index of 1.6774. From this, the fast axis is the polarization direction of the ordinary ray and the slow axis is the polarization direction of the extraordinary ray.

  The wavelengths of the ordinary and extraordinary rays in the crystal are 116.001 nm and 115.056 nm, respectively, because the wavelength in vacuum (193 nm) is divided by the respective refractive index, and the wavelength in the crystal is one wavelength. Each time it travels, an optical path difference of 0.945 nm is formed between both light fluxes. Therefore, when traveling by 122.7 (=116.001/0.945) wavelengths, an optical path difference of about 1 wavelength is formed between both light fluxes. However, if the optical path difference is exactly one wavelength or an integer number of wavelengths, it is equivalent to that both light fluxes have substantially no optical path difference. The thickness of the crystal for 122.7 wavelength corresponds to 14239 nm, that is, 14.239 μm, according to the calculation of 122.7×193/1.6638. Similarly, in order to form a half-wavelength optical path difference between the ordinary ray and the extraordinary ray, the thickness of the crystal should be set to 7.12 μm, which is half the above.

From this, in order to form the first birefringent member 12 which is the first non-uniform wavelength plate with quartz, the thickness T1 of the central portion in the above formula (1) is set to an integral multiple of 14.239 μm, The thickness at the reference position (X=1) near the periphery may be increased by 7.12 μm, that is, the proportional coefficient α may be set to 7.12 μm.
At this time, the polarization phase difference ΔP1 formed by the first birefringent member 12 is expressed as a function of the position X in the X direction as follows.

ΔP1=0.5×(1.7×X ⁴ −0.7×X ² ) (2)
The thickness of the first birefringent member 12 is the distance between the entrance surface 12a and the exit surface 12b of the first birefringent member 12 as long as it satisfies the relationship between the thickness for forming the phase difference and the position in the X direction. For example, the shapes of the incident surface 12a and the exit surface 12b may be arbitrary. However, in terms of processing the surface shape, it is easier to process one of the surfaces as a flat surface. Therefore, as shown in FIG. 2B, it is actually preferable to make the exit surface 12b a flat surface. .. In this case, the value of the thickness TA of the entrance surface 12a when the value of the thickness TA on the exit surface 12b is set to 0 is the same as TA calculated by the equation (1). Of course, the incident surface 12a may be a flat surface.

  FIG. 4A is a diagram showing the relationship between the polarization phase difference ΔP1 (unit is the wavelength of the illumination light) and the position X, which is expressed by the equation (2). 5 is a diagram showing the polarization state of the illumination light emitted from the first birefringent member 12 of the present example. In FIG. 5, the polarization state of the illumination light distributed at each position on the XZ coordinate is , A line segment centering on each position, a circle, or an ellipse. The origins (X=0, Z=0) of the X-axis and the Z-axis in FIG. 5 are set at the center of the birefringent member 12, and the scales in the X-direction and the Z-direction are X=±1,Z. The positions of ±1 (both positions away from the origin X=0, Z=0 by the reference length) are set to be located at the four corners in FIG.

  At the position identified by each XZ coordinate in FIG. 5, the illumination light is in a polarization state whose main component is linearly polarized light at the position where the line segment is displayed, and the direction of the line segment indicates the polarization direction. At the position where the ellipse is displayed, the illumination light is in a polarization state whose main component is elliptically polarized light, and the long side direction of the ellipse indicates the direction in which the linearly polarized light component included in the elliptically polarized light is maximum. There is. Further, at the position where the circle is displayed, the illumination light is in a polarization state whose main component is circularly polarized light.

  As shown in FIG. 4A, the first birefringent member 12 functions as a so-called half-wave plate at a position ±1 away from the center in the X direction. Here, the illumination light IL emitted from the exposure light source 1 of FIG. 1 is mainly composed of linearly polarized light polarized in the X direction as described above, and this half-wave plate has its fast axis nf and slow axis. ns is rotated by 45° with respect to the X direction which is the polarization direction of the incident light (illumination light). Therefore, as shown in FIG. 5, the polarization state of the illumination light transmitted near the position of ±1 (reference length) in the X direction from the center of the first birefringent member 12 is By the action, it is converted into a polarization state whose main component is linearly polarized light in the Z direction.

Further, as shown in FIG. 4A, the polarization phase difference Δ1 is 0.25 for the illumination light that passes through the first birefringent member 12 in the vicinity of the position ±0.6 in the X direction from the center. Therefore, the first birefringent member 12 acts as a so-called quarter wave plate. Therefore, the illumination light transmitted through this portion is converted into a polarization state whose main component is circularly polarized light.
On the other hand, a light beam that passes through the center in the X direction has no optical path difference between the linearly polarized lights in the fast axis nf direction and the slow axis ns direction, so that the polarization state of the transmitted light is not converted. .. Therefore, the light flux that enters the birefringent member 12 at the center in the X direction exits the birefringent member 12 while maintaining the state where the linear polarization state in the X direction is the main component. Then, the light flux that transmits the positions other than the respective positions of X=0, ±0.6, and ±1 becomes a polarization state whose main component is elliptically polarized light having a different shape according to the position, and the first The light passes through the birefringent member 12. This polarization state is as shown in FIG.

In FIG. 1, the illumination light IL having a different polarization state depending on the place where the light passes through the first birefringent member 12 enters the second birefringent member 13. The second birefringent member 13 is also a disc-shaped member made of a birefringent material.
3A is a view of the second birefringent member 13 of FIG. 1 viewed in the +Y direction along the illumination system optical axis AX2, and unlike the above-described first birefringent member 12, FIG. As shown in A), the fast axis nf of the second birefringent member 13 is set parallel to the Z axis of the XZ coordinate which is the same coordinate axis as in FIG. 1, and the slow axis ns is set parallel to the X axis. .. The size (diameter) in the in-plane direction of the second birefringent member 13 is also larger than the luminous flux diameter of the illumination light IL at the position where the second birefringent member 13 is arranged.

  Also, the thickness of the second birefringent member 13 is not uniform, and the thickness thereof is in the direction of the function Z=X of the XZ coordinate system in FIG. 3A, that is, in FIG. 3A. It changes according to the position of the direction of the line BB' (hereinafter, referred to as "XZ direction"). 3B is a cross-sectional view of the second birefringent member 13 taken along the line BB′ of FIG. 3A. As shown in FIG. 3B, the birefringent member 13 has a left end portion ( The shape is thin in the vicinity of B) and thick in the right end portion (in the vicinity of B′). On the other hand, the thickness of the second birefringent member 13 is uniform in the direction orthogonal to the XZ direction. Therefore, the second birefringent member 13 also functions as a second non-uniform wavelength plate in which the phase difference between the polarized lights given to the transmitted light differs depending on the place.

In this example, the thickness TB of the second birefringent member 13 is represented by the following function for the position XZ in the XZ direction. As shown in FIG. 3B, the origin (XZ=0) in the XZ direction is the center of the birefringent member 13 (illumination system optical axis), and the thickness at the center is T2.
TB=T2+β×(2.5×XZ ⁵ −1.5×XZ ³ ) (3)
Here, β is a proportional coefficient, and like the thickness T2 of the central portion, the value of β differs depending on the difference in the refractive index between the fast axis and the slow axis of the birefringent material used. Here, the thickness T2 of the central portion is such that the phase difference ΔP2 between the polarizations of the second birefringent member 13 is 0.25 (the unit is the wavelength of the illumination light), that is, the central portion is a quarter wavelength plate. Set to function as.

Further, in the birefringent member 13, the polarization phase difference ΔP2 is set to +0.75 and −0.25, respectively, at positions +1 (reference length) and −1 apart in the XZ direction. This means forming a difference of +0.5 and −0.5 between polarizations with the center, respectively.
That is, in the second birefringent member 13 of this example, the thickness is set so that the inter-polarization phase difference ΔP2 is represented by the following equation.

ΔP2=0.25+0.5×(2.5×XZ ⁵ −1.5×XZ ³ ) (4)
When the second birefringent member 13 is also made of quartz similarly to the above example, the thickness T2 of the central portion is 14.239 μm times (an integer + 1/4) and the proportional coefficient β is 7 It may be set to 12 μm. FIG. 4B is a diagram showing the relationship between the polarization phase difference ΔP2 and the position XZ in the equation (4).

In FIG. 1, the illumination light having a different polarization state depending on the place transmitted through the first birefringent member 12 is converted again by the second birefringent member 13 depending on the place. The polarization state of the illumination light IL emitted from the second birefringent member 13 is shown in FIG.
The display method of FIG. 4C is similar to the display method of FIG. 5 described above. In FIG. 4C, the polarization state of the illumination light distributed at each position on the XZ coordinate is centered at each position. Is indicated by a line segment (linearly polarized light) or an ellipse (elliptically polarized light). The origins (X=0, Z=0) of the X-axis and the Z-axis in FIG. 4C are also set at the center of the birefringent member 13.

  As shown in FIG. 1, in the present embodiment, the first birefringent member 12 and the second birefringent member 13 are arranged immediately in front of the fly-eye lens 14, and at the exit side of the fly-eye lens 14. The surface is arranged near the pupil plane 15 in the illumination optical system ILS. Therefore, the first birefringent member 12 and the second birefringent member 13 are arranged at positions substantially equivalent to the pupil image 15 in the illumination optical system ILS.

  Therefore, the illumination light IL that has passed through the first birefringent member 12 and the second birefringent member 13 is incident on the reticle R at an incident angle and an incident direction that are determined depending on its position. That is, in FIG. 4C, the light flux distributed on the origin (the position of X=0, Z=0) is incident vertically on the reticle R, and the light flux distributed at the position apart from the origin by a predetermined distance is at this distance. And is incident on the reticle R at an angle of incidence substantially proportional to. Further, the incident direction is the direction equal to the azimuth angle from the origin of the point.

  The outer circle C1 and the inner circle C2 shown in FIGS. 4C and 5 are boundaries of the distribution of illumination light for forming a predetermined annular illumination on the reticle R. The radii of the circles C1 and C2 are the same as those of the outer circle C1 with the reference length used in the determination of the thickness shape (thickness distribution) of the first birefringent member 12 and the second birefringent member 13 as a unit. The radius is 1.15 and the radius of the inner circle C2 is 0.85. That is, the annular zone ratio (radius of the inner circle/radius of the outer circle) of the annular illumination is assumed to be 0.74. This is based on the assumption of commonly used so-called "3/4 annular illumination (inner radius: outer radius=3:4)", but of course the conditions of the annular illumination to which the present invention should be applied. Is not limited to this.

As is clear from FIG. 4C, the illumination light emitted from the second birefringent member 13 is identified in the specific annular zone region 36 which is an annular zone surrounded by the outer circle C1 and the inner circle C2. The polarization state is mainly composed of linearly polarized light whose polarization direction is the circumferential direction of the ring zone region 36.
Comparing FIG. 4C and FIG. 5, the polarization states of the illumination light on the X axis and the Z axis are almost equal. However, the polarization state at a position about 45° away from each axis around the origin (the upper right position, the upper left position, the lower left position, and the lower right position in FIG. 4C) is almost circular polarization in FIG. On the other hand, in FIG. 4C, the linearly polarized light in the circumferential direction of the specific ring zone region is converted. This is due to the action of the second birefringent member 13, and the second birefringent member 13 functions as a quarter wavelength plate in the upper left and lower right regions in FIG. The upper right region and the upper right region respectively function as a -1/4 wave plate and an equivalent 3/4 wave plate.

  In an actual exposure apparatus, the actual radius of the outer circle C1 of the specific ring zone region 36 is the numerical aperture (NA) on the reticle R side of the projection optical system 25 in FIG. 1, the relay lens in the illumination optical system ILS. It is determined by the focal length of the optical system including 16 and the condenser lenses 18 and 20, and the value of the coherence factor (illumination σ) to be set, and the radius of the inner circle C2 is a value determined by the annular zone ratio to be further set. Then, with respect to the condition of the annular zone illumination, the first birefringent member is so arranged that the polarization direction of the illumination light distributed in the specific annular zone area 36 matches the circumferential direction of the annular zone at each position. It goes without saying that the thickness shapes of 12 and the second birefringent member 13 will be determined.

Here, to determine the thickness shapes of the first birefringent member 12 and the second birefringent member 13 means that the shapes are proportionally enlarged or proportionally reduced in the XZ plane, and in the Y direction (light traveling direction). Means that the amount of unevenness is not changed.
As described above, in the first embodiment of the first and second birefringent members 12 and 13, there is no light quantity loss of the illumination light flux due to the first and second non-uniform wavelength plates that do not dimm the light flux. Thus, the polarization direction of the illumination light distributed in the specific ring zone area can be matched with the circumferential direction of the ring zone area at each position. In this case, of the illumination light, the illumination light that passes through the specific ring zone region 36 and is applied to the reticle R, that is, the specific illumination light that is applied to the reticle R within a specific incident angle range, has a polarization direction. Is a light in a polarization state whose main component is S-polarized light in a direction perpendicular to the incident surface. This may improve the contrast, resolution, depth of focus, etc. of the transferred image due to the periodicity of the pattern to be transferred (details will be described later).

Next, a second embodiment of the first and second birefringent members 12 and 13 in the illumination optical system ILS of FIG. 1 will be described with reference to FIG.
Also in this example, the configurations of the first birefringent member 12 and the second birefringent member 13 are basically the same as those shown in the above-mentioned first embodiment. That is, the first birefringent member 12 has the fast axis direction and the thickness shape as shown in FIGS. 2A and 2B, and the second birefringent member 13 is 3(A), and the shape of the fast axis and the thickness as shown in FIG. 3(B). However, in this example, the form of the function relating to the thickness of the birefringent members 12 and 13 is changed.

FIG. 6A corresponds to FIG. 4A and shows the characteristic of the phase difference ΔP1 between polarizations formed by the first birefringent member 12 in the second embodiment with respect to the position in the X direction. The polarization phase difference ΔP1 in FIG. 6A is a function including a trigonometric function regarding the position X as described below.
ΔP1=0.265×{1-cos(π×X ² )} (5)
Such an inter-polarization phase difference ΔP1 can be realized by expressing the thickness TA of the first birefringent member 12 with respect to the position X in the X direction by the following function.

TA=T1+γ×{1-cos(π×X ² )} (6)
Here, γ is a proportional coefficient. Similar to the first embodiment, when the first birefringent member 12 is formed of quartz, the central thickness T1 may be set to an integral multiple of 14.239 μm and the proportional coefficient γ may be set to 3.77 μm. .. 3.77 μm is a value obtained by multiplying the crystal thickness of 14.239 μm, which gives a phase difference between polarized lights of one wavelength, by 0.265, which is a coefficient multiple of the above formula (5).

FIG. 6B shows the characteristic of the phase difference ΔP2 between polarizations formed by the second birefringent member 13 in the second example with respect to the position in the XZ direction. The polarization phase difference ΔP2 in FIG. 6B can be represented by a function including a trigonometric function regarding the position XZ as follows.
ΔP2=0.25+0.5×sin(0.5×π×XZ ³ ) (7)
Such a phase difference ΔP2 between polarized lights can be realized by expressing the thickness TB of the second birefringent member 13 by the following function with respect to the position XZ in the XZ direction.

TB=T2+δ×sin (0.5×π×XZ ³ ) (8)
Here, δ is a proportional coefficient. When the second birefringent member 13 is made of quartz, the central thickness T2 may be set to (integral+1/4) times 14.239 μm, and the proportional coefficient δ may be set to 7.12 μm.
Also in this example, the first birefringent member 12 and the second birefringent member 13 function as first and second non-uniform wave plates in which the phase difference between polarized lights given to transmitted light differs depending on the location. To do. Then, the linearly polarized light that is polarized in the X direction and is incident on the first birefringent member 12 is converted into the polarization distribution shown in FIG. 6C and is emitted from the second birefringent member 13.

  As can be seen by comparing FIG. 6C and FIG. 4C, the first birefringent member 12 and the second birefringent member 13 of the second embodiment are the same as those of the first embodiment. The polarization state of the illumination light distributed in the specific annular zone 36 surrounded by the outer circle C1 and the inner circle C2 can be made closer to the linearly polarized light parallel to the circumferential direction than that shown. This is because the first birefringent member 12 and the second birefringent member 13 of the second embodiment adopt a thickness shape (that is, a surface shape) determined by a higher-order function called a trigonometric function. This is because more precise polarization control can be performed.

However, since the first birefringent member 12 and the second birefringent member 13 shown in the first embodiment are composed of functions up to the fifth order at most, the polarization control characteristics are slightly inferior, but they are easy to process. Therefore, there is an advantage that the manufacturing cost can be kept low.
In order to further reduce the manufacturing cost of the first and second birefringent members 12 and 13, for example, the surface shape of the first birefringent member 12 is a cylindrical surface (a surface having a circular cross section in the X direction). The surface shape of the second birefringent member 13 may be a taper surface (inclined flat surface). The polarization control characteristic in this case is deteriorated as compared with that of the first embodiment, but the effect can be sufficiently obtained depending on the application of the projection exposure apparatus, and the manufacturing cost can be reduced and high performance can be obtained. An exposure apparatus can be realized.

In this way, by making the surface shape of the second birefringent member 13 a tapered surface, the phase difference between the polarizations of the light flux transmitted through the second birefringent member 13 is within the plane of the second birefringent member 13. It means that it is determined linearly (a linear function) according to the position.
By the way, the shapes of the first birefringent member 12 and the second birefringent member 13 in FIG. 1 are not limited to the shapes shown in the above-mentioned first and second embodiments, and the above-mentioned transmitted light thereof is Any shape may be used as long as the polarization state in the specific ring zone region can be matched in the circumferential direction in each part.

  For example, the shapes of the first birefringent member 12 and the second birefringent member 13 are not the shapes represented by the functions that are continuous and differentially continuous as described above, but are stepwise in which the shapes gradually change at a predetermined position. The shape may be. Further, instead of a mechanical or mechanochemical polishing method, etching is suitable for forming such a step-like shape.

  In order to realize such a polarization state, when the polarization state of the light beam incident on the first birefringent member 12 is illumination light having a single polarization state whose main component is linear polarization, The first birefringent member 12 is preferably one that gives a phase difference between polarizations having two-fold rotational symmetry about the illumination system optical axis AX2. It goes without saying that this includes a non-uniform wave plate having an even function thickness in the X direction and a constant thickness in the Y direction, as shown in the first and second embodiments above. There is no.

  Further, the second birefringent member 13 is preferably a non-uniform wavelength plate having a one-time rotational symmetry about the illumination system optical axis AX2 and giving a phase difference between polarized lights. The one-time rotational symmetry means that the distribution of the phase difference between polarizations is substantially symmetric about one of the two axes orthogonal to each other in the illumination system optical axis AX2 and is substantially opposite about the other axis. Say that it is a name. Antisymmetry generally means a function whose absolute value is the same with respect to the inversion of the coordinate axis but whose sign is inverted, but here it is assumed that a function that adds a constant offset to a general antisymmetric function is also included. .. This is a non-uniform wave plate having a thickness determined by an odd function with an offset in the XZ direction and having a constant thickness in the direction orthogonal thereto, as shown in the first and second embodiments. It goes without saying that it is included.

Further, in the present embodiment, it is particularly important to set the illumination light distributed in the specific ring zone region to a predetermined polarization state, so that the first birefringent member 12 and the second birefringent member 12 It goes without saying that, with regard to the shape of 13 as well, there is no particular problem even if the shape does not satisfy the above-mentioned conditions in the portion that does not correspond to the specific ring zone region.
The number and the fast axis direction of the first birefringent member 12 and the second birefringent member 13 are not limited to those shown in the first and second embodiments. That is, three or more birefringent members may be arranged in series along the traveling direction of the illumination light (along the optical axis AX2 of the illumination system), and rotation about the optical axis AX2 in the fast axis direction may be performed. The relationship is not limited to 45°. Further, when three or more birefringent members are arranged in series along the traveling direction of the illumination light, at least a part of the specific ring zone area, and preferably substantially the entire circumference area thereof. In order to make the polarization state of the illumination light into linearly polarized light that is substantially parallel to the circumferential direction, the direction of the fast axis of at least one birefringent member among the plurality of birefringent members is It may be different from the direction of the fast axis.

Similarly, the material of the birefringent members 12, 13 and the like is not limited to the above-mentioned crystal, but other birefringent materials may be used, and it is formed by utilizing the intrinsic birefringence of fluorite. You can also do it. Further, it is also possible to use, as the birefringent members 12 and 13 and the like, a material such as synthetic quartz, which originally has no birefringence, having a birefringence by applying stress or the like.
Furthermore, as the birefringent members 12 and 13, it is also possible to use a transparent substrate having no birefringence and a material having a birefringence bonded thereto. In this case, it goes without saying that the above-mentioned thickness refers to the thickness of the birefringent material. Here, the bonding is not limited to mechanical joining such as adhesion and pressure bonding, and may be a method of forming a thin film having birefringence on a transparent substrate by means of vapor deposition or the like. .. As described above, the thickness and the like of the first birefringent member 12 and the second birefringent member 13 shown in the first and second embodiments vary depending on the magnitude of the birefringence of the material used. However, it goes without saying that the shape determination method described above can be applied and the shape is determined even when a material other than quartz is used.

Here, regarding the above-described annular illumination, the advantages of the illumination light in which the polarization state of the illumination light distributed in the annular zone matches the circumferential direction of the annular zone will be described with reference to FIGS. A brief explanation will be given with reference to.
FIG. 7A shows an example of a fine periodic pattern PX formed on the reticle R of FIG. The periodic pattern PX is a pattern having periodicity in the X direction in the same XYZ coordinate system as in FIG. 1, and its pitch PT is set on the scale on the wafer W in consideration of the projection magnification of the projection optical system 25 in FIG. The converted value is 140 nm. FIG. 7B shows the wafer side when this pattern is illuminated with annular light having a coherence factor (illumination σ) of 0.9 and an annular ratio of 0.74 using illumination light having a wavelength of 193 nm. 2 shows the distribution of diffracted light formed in the pupil plane 26 (see FIG. 1) of the projection optical system 25 having a numerical aperture (NA) of 0.90.

  FIG. 7C is a diagram showing the conditions of the annular illumination for illuminating the pattern PX. In the pupil plane 15 of the illumination optical system ILS of FIG. Illumination light from the area ILO illuminates the pattern PX. The 0th-order diffracted light D0 of FIG. 7B from the periodic pattern PX is entirely distributed in the pupil plane 26, passes through the projection optical system 25, and reaches the wafer W, but the 1st-order diffracted lights D1R and D1L are Only partially, the pupil plane 26 and the projection optical system 25 can be transmitted. The image of the pattern PX of the reticle R is formed on the wafer W as interference fringes of the 0th-order diffracted light D0 and the 1st-order diffracted lights D1R and D1L. The interference fringes are formed on the pupil plane of the illumination optical system ILS. It is limited to a pair of 0th-order diffracted light and 1st-order diffracted light generated from the illumination light emitted from the same position in 15.

  In FIG. 7B, the 1st-order diffracted light D1L located at the left end of the pupil plane 26 forms a pair with the part of the 0th-order diffracted light D0 located at the right end, and these diffracted lights are shown in FIG. Illumination light illuminated from the rightmost partial region ILR in the annular zone region IL0 in C). On the other hand, in FIG. 7B, the 1st-order diffracted light D1R located at the right end of the pupil plane 26 forms a pair with the part of the 0th-order diffracted light D0 located at the left end, and these diffracted lights are shown in FIG. It is the illumination light illuminated from the leftmost partial area ILL in the annular zone IL0 in 7(C).

  That is, when exposing the pattern PX having such a fine pitch in the X direction, of the illumination light emitted from the annular zone IL0 on the pupil plane 15 of the illumination optical system ILS, it contributes to the image formation of the pattern PX. The light flux is limited to the partial region ILR and the partial region ILL, and the illumination light emitted from other regions in the annular region IL0 is the illumination light that does not contribute to the image formation of the pattern PX.

  By the way, when exposing a pattern having a periodicity in the X direction and a longitudinal direction in the Y direction like the pattern PX, when the reticle R is illuminated with linearly polarized light having a polarization direction in the Y direction, the contrast of the projected image is increased. It is reported in Non-Patent Document 1 (Thimothy A. Brunner, et al.: "High NA Lithographic imaging at Brewster's ange1", SPIE Vo1.4691, pp.1-24 (2002)) and the like mentioned above. ing.

  Therefore, the illumination light distributed in the partial region ILR and the partial region ILL of FIG. 7C is respectively converted into the PR direction and the PL direction (action of the mirror 19 in FIG. 1) parallel to the Z direction in FIG. 7C. Considering the above, linearly polarized light polarized in the reticle R (corresponding to the Y direction) is effective for improving the contrast of the projected image of the pattern PX, and thus for improving the resolution and the depth of focus.

  Next, when the reticle pattern is a periodic pattern rotated by 90° with respect to the pattern PX of FIG. 7A and having a fine pitch in the Y direction, the diffracted light distribution shown in FIG. 7B is also 90°. It will rotate. As a result, the partial area through which the illumination light that contributes to the image formation of the periodic pattern passes is also rotated by 90° from the partial area ILR and the partial area ILL shown in FIG. 7C (that is, in FIG. 7C). And the preferred polarization state is linearly polarized light whose polarization direction coincides with the X direction. As described above, when the reticle R including both the pattern PX having a fine periodicity in the X direction and the pattern PY having a fine periodicity in the Y direction is exposed, it has a polarization state as shown in FIG. Use of illumination light is effective.

  FIG. 8A is a perspective view showing the relationship between the pupil plane 15 of the illumination optical system ILS of FIG. 1 and the reticle R in a simplified manner. The relay lens 16, the condenser lenses 18 and 20 in FIG. Omitted. As described above, in order to improve the imaging performance of the pattern PX having the periodicity in the X direction, the illumination light distributed in the annular zone IL0 in FIG. 8A has its end portion ILL in the X direction, In the ILR, linearly polarized light in the Y direction (the depth direction of the paper surface of FIG. 8A) is desirable, and in order to improve the imaging performance of the pattern PY having the periodicity in the Y direction, its end portion in the Y direction. In ILU and ILD, linearly polarized light in the X direction is desirable. That is, it is desirable to use linearly polarized light whose polarization direction is substantially the same as the circumferential direction of the ring zone IL0.

Further, when the reticle R includes patterns not only in the X and Y directions but also in the intermediate directions (45° and 135° directions), the polarization direction of the reticle R is also taken into consideration in consideration of the directivity of these patterns. It is desirable to use linearly polarized light that exactly matches the circumferential direction of the area.
By the way, the above-mentioned polarization state does not always realize an effective polarization state with respect to the pattern orthogonal to the directional pattern suitable for the polarization state of each part in the annular zone IL0. For example, the illumination light polarized in the X direction from the partial region ILU is in a polarization state which is not preferable for forming an image of the pattern PX having the periodicity in the X direction and the longitudinal direction in the Y direction. However, as is clear from FIG. 7C showing the light source that contributes to the image formation of the pattern having a fine pitch in the X direction, in FIG. 7C, the partial area ILU corresponding to the upper end of the annular zone IL0 is Since the light source does not contribute to image formation of a pattern having a fine pitch in the X direction, no matter what the polarization state of the partial region ILU is, the image formation is caused by the polarization state. It does not deteriorate the characteristics at all.

  Note that, as shown in FIG. 8A, linearly polarized light that substantially coincides with the circumferential direction of the ring zone IL0 on the pupil plane 15 of the illumination optical system ILS is incident on the reticle R as so-called S-polarized light. S-polarized light means linearly polarized light whose polarization direction is orthogonal to the plane of incidence on which a light beam enters an object (a plane including the normal line of the object and the light beam). That is, as shown in FIG. 8B, the illumination light ILL1 from the partial region ILL, which is the linearly polarized light in the direction coinciding with the circumferential direction of the ring zone IL0, has the polarization direction EF1 as the incident surface (see FIG. It is incident on the reticle R as S-polarized light which is perpendicular to the paper surface of B). Further, also for the illumination light ILD1 on the similar partial region ILD, as shown in FIG. 8C, the reticle R is S-polarized light whose polarization direction EF2 is perpendicular to the incident surface (the paper surface of FIG. 8C). Incident on.

  As a matter of course, the illumination light from the partial regions ILR and ILU and the partial regions ILR and ILU at positions symmetrical with respect to the optical axis AX41 of the illumination optical system are also annular regions on the partial regions ILR and ILU. Since it has a polarization direction that coincides with the circumferential direction of IL0, it also becomes S-polarized light due to its symmetry and enters the reticle R. As a general property of the annular illumination, the incident angle of the illumination light distributed on the annular region IL0 to the reticle R is centered at an angle φ from the optical axis AX41 of the illumination optical system (that is, a perpendicular to the reticle R). It becomes a predetermined angle range. The light flux irradiated onto the reticle R at this incident angle will be referred to as "specific illumination light" below. The angle φ and the angle range may be determined based on the wavelength of the illumination light, the pitch of the pattern to be transferred on the reticle R, and the like.

By the way, the above-mentioned first and second birefringent members 12 and 13 have a specific ring zone between a predetermined outer radius (outer circle C1) and inner radius (inner circle C2) determined by the shape peculiar to the members. The polarization state of the illumination light distributed in the area is converted into a polarization state whose main component is linearly polarized light parallel to the circumferential direction of the specific ring zone area, but its radius (C2, C1) can be easily changed. Is difficult.
Therefore, as described above, when it is necessary to change the desired annular zone based on the pitch of the pattern to be transferred on the reticle R, etc., the first and second birefringent members 12, As shown in FIG. 9, it is desirable to provide a plurality of zoom-type conical prisms 41 and 42 between the optical disc 13 and the optical integrator such as the fly-eye lens 14 to make the radius of the specific ring zone region variable. .. In FIG. 9, a plurality of zoom-type conical prisms are a concave conical prism 41 having a concave conical surface 41b and a convex conical prism 42 having a convex conical surface 42a, and the distance DD is made variable to illuminate system light. It is arranged along the axis AX2.

  In this case, the illumination light transmitted through the first and second birefringent members 12 and 13 and distributed in the specific annular zone centered on the average radius RI is caused by the zoom conical prisms 41 and 42 to fly eye lens. In a pupil plane 15 of the illumination optical system, which is the entrance surface of 14 and the exit surface thereof, the radius is expanded to RO. The radius RO can be increased by increasing the distance DD between the conical prisms 41 and 42, and can be reduced by decreasing the distance DD.

As a result, in the pupil plane 15 of the illumination optical system, it is possible to form a specific annular zone region in which the illumination light composed of linearly polarized light parallel to the circumferential direction is distributed, with an arbitrary radius, and the illumination of the annular illumination. The condition can be changed according to the pattern on the reticle R to be transferred.
It is needless to say that a zoom optical system may be used instead of the zoom type conical prisms 41 and 42.

  By the way, in the above-mentioned embodiment, the explanation is made on the premise that the illumination light amount distribution formed on the pupil plane 15 of the illumination optical system ILS in FIG. 1 is a ring zone region, that is, it is applied to the ring zone illumination. The illumination condition that can be realized by the first projection exposure apparatus is not necessarily limited to the annular illumination. That is, the birefringent members 12 and 13 of FIG. 1 and the zoom-type conical prisms 41 and 42 of FIG. Therefore, even if the distribution of the illumination light is limited to a further specific partial area within the specific annular zone area, that is, for example, the partial area ILL in FIG. 7C, Even in the case of being limited to the ILR, it is possible to convert the illumination light distributed in the partial area into illumination light mainly composed of linearly polarized light having a polarization direction parallel to the circumferential direction of the specific ring zone area. Needless to say.

As described above, in order to collect the illumination light only in a specific area within the specific ring zone area, the diffractive optical element 9a in FIG. 1 is replaced and the diffracted light (illumination light generated from another diffractive optical element is used. Light) may be concentrated in a more specific discrete area in the specific annular zone area on the first birefringent member 12 and the second birefringent member 13. The illumination light is concentrated at two locations, for example, the partial areas ILL and ILR in FIG. 7C, but is not limited to this and may be concentrated at any location in the specific ring zone area. Also, the number may be four. The selection may be made according to the shape of the pattern to be exposed on the reticle R.
When the illumination light is concentrated in a specific area within the specific ring zone area, a convex polyhedral prism such as a pyramid shape prism is used instead of the above-described zoom type conical prisms 41 and 42. It is also possible to use an optical member group in which a concave polyhedron prism is also combined in a variable manner.

  Since the illumination light distributed outside these specific areas is not suitable for the exposure of the above-mentioned pattern to be exposed, it may be preferable to make the light quantity distribution substantially zero. On the other hand, depending on the manufacturing error of the diffractive optical element 9a or the like, diffracted light (hereinafter referred to as “error light”) is generated from the diffractive optical element 9a or the like in a direction other than the desired direction, and illumination is applied to areas other than the partial areas. Light may be distributed. Therefore, for example, a configuration may be adopted in which a stop is provided on the incident surface side or the exit surface side of the fly-eye lens 14 in FIG. 1 to block this error light. As a result, the illumination light amount distributions of the plurality of specific areas are completely discrete. However, a pattern other than the pattern to be exposed is also present on the reticle R, and the error light may be effective in forming an image of a pattern other than the target. In some cases, it is not necessary to make the distribution zero.

  By the way, focusing on the incidence of the illumination light on the reticle R, limiting the distribution of the illumination light amount on the pupil plane 15 to a more specific area within the specific annular area means that the incident angle of the annular illumination is In addition to the range limitation, the incident direction is limited only from the plurality of substantially discrete directions. As a matter of course, even when the present invention is applied to the annular illumination, the error light distributed outside the specific annular region is shielded by providing a stop on the incident surface side or the exit surface side of the fly-eye lens 14. be able to.

  Although the fly-eye lens 14 is used as the optical integrator in the above embodiments, an internal reflection type integrator (for example, a glass rod) may be used as the optical integrator. In this case, the exit surface of the glass rod is arranged not on the pupil plane 14 of the illumination optical system but on the conjugate plane with the reticle R.

  Further, in the above embodiment, the laser light source as the exposure light source 1 emits linearly polarized light polarized in the X direction. However, depending on the form of the laser light source, it is polarized in the Z direction in FIG. There may be a case where linearly polarized light or a light beam having another polarization state is emitted. In the case where the exposure light source 1 in FIG. 1 emits light linearly polarized in the Y direction, that is, light linearly polarized in the Z direction at the positions of the birefringent members 12 and 13, the first and second embodiments described above are used. By rotating the birefringent members 12 and 13 shown in FIG. 9 by 90° about the optical axis AX2 of the illumination system, a polarization state substantially similar to the polarization state shown in FIGS. 4C and 6C is obtained. It is possible to obtain illumination light (more precisely, illumination light obtained by rotating the state shown in both figures by 90°).

  Alternatively, the polarization control member 4 (polarization control mechanism) in FIG. 1 may convert the Y-direction linearly polarized light emitted from the exposure light source 1 into the X-direction linearly polarized light. Such a polarization control member 4 can be easily realized by a so-called half-wave plate. Even when the exposure light source 1 emits circularly polarized light or elliptically polarized light, similarly, by using a ½ wavelength plate or a ¼ wavelength plate as the polarization control member 4, linearly polarized light in a desired Z direction can be obtained. Can be converted to.

  However, the polarization control member 4 cannot convert the light flux of any polarization state emitted from the exposure light source 1 into the Z-direction polarization without loss of light amount. Therefore, the exposure light source 1 needs to generate a light beam having a single polarization state such as a linearly polarized light, a circularly polarized light, and an elliptically polarized light (a light beam that can be converted into a linearly polarized light by a wavelength plate or the like without loss of light amount). However, if the intensity of the light flux other than the single polarization state is not so large with respect to the overall intensity of the illumination light, the adverse effect on the imaging characteristics of the light flux other than the single polarization state is slight. Therefore, up to a certain level (for example, about 20% or less of the total amount of light), the light flux emitted from the exposure light source 1 may include a light flux other than the single polarization state.

  In consideration of the use state of the projection exposure apparatus of the above-described embodiment, the polarization state of the illumination light is always linearly polarized with the illumination light distributed in the specific ring zone area being substantially parallel to the circumferential direction of the ring zone area. Alternatively, it is not always best to set the specific illumination light to enter the reticle R as S-polarized light. That is, depending on the pattern of the reticle R to be exposed, it may be preferable to use normal illumination (illumination having a circular illumination light amount distribution on the pupil plane 15 of the illumination optical system) instead of the annular illumination. In some cases, it may be preferable not to use the illumination light having the polarization state of the above embodiment.

Therefore, in order to cope with such a situation of use, an element or an optical element which can convert the polarization state of the light beam emitted from the light source such as a laser into a random polarization or the like as the polarization control member 4 in FIG. A system should be adopted. This can be realized by, for example, two polarization beam splitters 4b and 4c as shown in FIG.
FIG. 10 shows a polarization control optical system that can be installed at the position of the polarization control member 4 in FIG. 1. In FIG. 10, an illumination light flux IL0 (corresponding to the illumination light IL in FIG. 1) composed of, for example, linearly polarized light is The light is incident on the rotating wave plate 4a composed of a half wave plate or a quarter wave plate. As a result, the illumination light beam IL1 converted into the linearly polarized light or the circularly polarized light in the direction inclined by 45° from the paper surface of FIG. 10 is the light beam IL2 and the S polarized light having the P polarization component with respect to the split surface by the first polarization beam splitter 4b. The light beam IL2 is divided into a component IL3, one light beam IL2 travels straight upward in the prism 4b in FIG. 10, and the other light beam IL3 is reflected rightward in FIG.

  The light beam IL2 that has traveled straight is incident on the next polarization beam splitter 4c, but due to its polarization characteristics, the light beam IL2 travels straight in the polarization beam splitter 4c and becomes a light beam IL4 that travels upward in FIG. On the other hand, the reflected light flux IL3 is reflected by the mirrors 4d and 4e and then enters the polarization beam splitter 4c, and the light flux IL3 reflected again here joins again with the straight-traveling light flux IL4. At this time, if the distance between the polarization beam splitters 4b and 4c and the mirrors 4d and 4e is DL, respectively, an optical path length difference of 2×DL is formed between the combined light beams IL3 and IL4. If the optical path length difference 2×DL is set longer than the coherent length of the illumination light flux, the coherence between the two light fluxes disappears, so that the merged light fluxes can be substantially randomly polarized.

  If such a polarization control optical system is loaded into the illumination optical system ILS of FIG. 1, the illumination light IL transmitted therethrough will always be randomly polarized light, which is an obstacle to realizing the polarization state of the above embodiment. It can happen. However, in the optical system shown in FIG. 10, by rotating the rotation wavelength plate 4a, the polarization state of the illumination light IL1 that has passed through the rotation wavelength plate 4a is converted into linearly polarized light that all passes through the first beam splitter 4b. As a result, the above obstacles do not occur in principle. However, a certain amount of light loss due to absorption in the polarization beam splitters 4b and 4c and reflection loss in the mirrors 4d and 4e cannot be avoided. Therefore, when the illumination light does not need to be randomly polarized, the beam splitter is used. A mechanism for retracting the 4b and 4c and the rotating wave plate 4a outside the optical path of the illumination optical system may be provided.

  By the way, even if such a polarization beam splitter is not used, it is possible to obtain substantially the same effect as the random polarized illumination by the following simple method. This is because the polarization state of the illumination light IL incident on the first birefringent member 12 in FIG. 1 is set to a direction 45° away from the X direction and the Z direction in FIG. This can be realized by converting the distributed illumination light into circularly polarized light. Therefore, when the projection exposure apparatus of the present embodiment is used for the purpose in which circularly polarized light can be regarded as approximately randomly polarized light, that is, when the required imaging performance is relatively loose, The polarization control member 4 in the inside is composed of, for example, a half-wave plate, and the polarization state of the illumination light incident on the first birefringent member 12 is set to a direction inclined by 45° from the X axis and the Z axis as described above. By doing so, it is possible to obtain almost the same effect as the randomly polarized illumination. Similarly, the polarization control member 4 may be formed of, for example, a 1/4 wavelength plate, and the polarization state of the illumination light incident on the first birefringent member 12 may be changed to circularly polarized light. You can also get the effect.

Alternatively, a mechanism that allows the first birefringent member 12 and the second birefringent member 13 in FIG. 1 to be collectively rotated about the illumination system optical axis AX2 that is the optical axis of the illumination optical system ILS, Even if the relationship between the birefringent members 12 and 13 and the direction of the linearly polarized light of the illumination light is rotated by, for example, 45°, the same effect as the randomly polarized illumination can be obtained.
By the way, also in the above-mentioned normal illumination, it may be preferable to set the polarization state to linearly polarized light in one predetermined direction. In the projection exposure apparatus of the above-described embodiment, in order to cope with such an illumination condition, the respective birefringent members such as the first birefringent member 12 and the second birefringent member 13 in FIG. Is provided with a mechanism for collectively rotating about the illumination system optical axis AX2 so that the fast axis (or slow axis) of each birefringent member is parallel to the direction of linear polarization of the illumination light. The rotation direction of the birefringent member may be set. In this case, the illumination light does not undergo any polarization state conversion action even when traveling through each birefringent member, and is emitted while maintaining the linearly polarized light at the time of incidence.

  When setting the linearly polarized state in one predetermined direction, the first birefringent member 12 and the second birefringent member 13 may be collectively retracted out of the optical path of the illumination optical system. Is. That is, an exchange mechanism may be provided, and the birefringent members and the like may be collectively exchanged to set the linearly polarized state in one predetermined direction. If an exchange mechanism is provided, a plurality of sets of birefringent member groups in the exchange mechanism can be set, and they can be exchangeably arranged on a position on the illumination system optical axis AX2. In this case, it is preferable that each birefringent member group has a property of converting illumination light into linearly polarized light along the circumferential direction in a specific ring zone region having a different outer radius and inner radius. Needless to say.

By the way, it is preferable to use the linearly polarized illumination light in one predetermined direction as described above, for example, when exposing a spatial frequency modulation type phase shift reticle in which pattern directions are aligned. In this case, the coherence factor (σ value) of the illumination light is preferably about 0.4 or less in order to further improve the resolution and the depth of focus of the pattern transferred by exposure.
Here, the operation of the birefringent members (the first birefringent member 12 and the second birefringent member 13) according to the present invention will be reconsidered with reference to FIGS. 4C and 6C. As shown in FIGS. 4A and 4B, the first birefringent member 12 and the second birefringent member 13 of the first embodiment (FIG. 4C) and the second embodiment (FIG. 6C) are both , Illumination light distributed inside a circle (not shown) centered on the optical axis (X=0, Z=0) of the illumination optical system and having a radius of about half the outer radius C1 of the specific ring zone region It can be seen that there is almost no effect on the polarization state of.

  Assuming that the radius of the outer radius C1 corresponds to, for example, 0.9 as the illumination σ (σ value), within the range of the illumination luminous flux of the illumination σ=0.45, the first birefringent member 12 and the second birefringent member 12 are included. The refracting member 13 emits the incident linearly polarized light in the X direction while maintaining the almost same polarization state. When linearly polarized light (Z-polarized light) in the Z direction is incident on the first birefringent member 12, the above illumination σ=0.45 is included in the light flux emitted from the second birefringent member 13. The polarization state of the light flux can be Z-polarized.

Therefore, if the birefringent members (the first birefringent member 12 and the second birefringent member 13) as in the first and second embodiments are used, they are retracted out of the optical path of the illumination optical system. Without switching the polarization direction of the incident light on the birefringent member by the polarization control member 4 or the like, an illumination σ suitable for illuminating the spatial frequency modulation type phase shift reticle is 0.4. It is possible to realize illumination light having an illumination light flux of not more than a certain degree and having polarized light in the X direction or the Z direction (polarized light in the X direction or the Y direction on the reticle R in FIG. 1, respectively).
Of course, in this case as well, it is needless to say that in order to limit the illumination σ to about 0.4, it is preferable to use the diffractive optical element 9a so that the directional characteristics of the generated diffracted light have an angular distribution corresponding thereto. Yes. Accordingly, it is also an advantage of the present invention that it is possible to form illumination luminous fluxes having various practical polarization states without providing the collective exchange mechanism.

Next, an example of a manufacturing process of a semiconductor device using the projection exposure apparatus of the above embodiment will be described with reference to FIG.
FIG. 11 shows an example of a semiconductor device manufacturing process. In FIG. 11, a wafer W is first manufactured from a silicon semiconductor or the like. After that, a photoresist is applied on the wafer W (step S10), and in the next step S12, a reticle (provisionally R1) is loaded on the reticle stage of the projection exposure apparatus of the above embodiment (FIG. 1), The wafer W is loaded on the wafer stage, and the pattern (represented by symbol A) of the reticle R1 is transferred (exposed) onto the entire shot area SE on the wafer W by the scanning exposure method. At this time, double exposure is performed if necessary. The wafer W is, for example, a wafer having a diameter of 300 mm (12 inch wafer), and the size of the shot area SE is, for example, a rectangular area having a width of 25 mm in the non-scanning direction and a width of 33 mm in the scanning direction. Next, in step S14, a predetermined pattern is formed in each shot region SE of the wafer W by performing development, etching, ion implantation and the like.

  Next, in step S16, a photoresist is coated on the wafer W, and then in step S18, a reticle (provisionally R2) is loaded on the reticle stage of the projection exposure apparatus of the above-described embodiment (FIG. 1). The wafer W is loaded on the wafer stage, and the pattern of the reticle R2 (denoted by the symbol B) is transferred (exposed) onto each shot area SE on the wafer W by the scanning exposure method. Then, in step S20, a predetermined pattern is formed in each shot region of the wafer W by performing development and etching of the wafer W, ion implantation, and the like.

  The above exposure process to pattern formation process (steps S16 to S20) are repeated as many times as necessary to manufacture a desired semiconductor device. Then, the semiconductor device SP as a product is manufactured through a dicing process (step S22) for separating each chip CP on the wafer W one by one, a bonding process, a packaging process, and the like (step S24). ..

  According to the device manufacturing method of this example, since exposure is performed by the projection exposure apparatus of the above-described embodiment, in the exposure process, the reticle is polarized in a predetermined polarization state while improving the utilization efficiency of illumination light (exposure beam). Can be illuminated. Therefore, since the resolution of the periodic pattern having a fine pitch is improved, it is possible to manufacture a semiconductor integrated circuit with higher integration and higher performance at low cost with high throughput.

  Further, in the projection exposure apparatus of the above-described embodiment, the illumination optical system and the projection optical system composed of a plurality of lenses are incorporated in the exposure apparatus main body to perform optical adjustment, and a reticle stage and a wafer stage composed of a large number of mechanical parts are provided. It can be manufactured by mounting it on the exposure apparatus main body, connecting wiring and piping, and further performing comprehensive adjustment (electrical adjustment, operation check, etc.). It is desirable that the projection exposure apparatus be manufactured in a clean room in which the temperature and cleanliness are controlled.

Further, the present invention can be applied not only to a scanning exposure type projection exposure apparatus, but also to a collective exposure type projection exposure apparatus such as a stepper. Further, the magnification of the projection optical system used is not limited to reduction magnification, but may be equal magnification or enlargement magnification. Furthermore, the present invention can be applied to the liquid immersion exposure apparatus disclosed in, for example, International Publication (WO) 99/49504.
Further, the application of the projection exposure apparatus of the present invention is not limited to the exposure apparatus for manufacturing a semiconductor device, and for example, for a liquid crystal display element formed on a rectangular glass plate, or a display device such as a plasma display. It can be widely applied to an exposure apparatus and an exposure apparatus for manufacturing various devices such as an image pickup device (CCD or the like), a micromachine, a thin film magnetic head, a DNA chip and the like. Further, the present invention is also applied to an exposure process (exposure apparatus) when manufacturing a mask (a photomask including an X-ray mask, a reticle, etc.) on which mask patterns of various devices are formed by using a photolithography process. be able to.

Further, it goes without saying that the illumination optical system (2 to 20) included in the projection exposure apparatus shown in the above embodiment can be applied as an illumination optical apparatus for illuminating the first object such as the reticle R. There is no.
It should be noted that the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention. In addition, all the disclosure contents of Japanese Patent Application No. 2003-376963 filed on October 28, 2003, including the specification, claims, drawings, and abstract, are incorporated herein by reference in their entirety. ..

  According to the device manufacturing method of the present invention, the utilization efficiency of the exposure beam (illumination light) can be improved, and the predetermined pattern can be formed with high accuracy. Therefore, various devices such as semiconductor integrated circuits can be manufactured with high accuracy and high processing capacity (throughput).

Claims (42)

A projection exposure apparatus comprising: an illumination optical system that illuminates illumination light from a light source onto a first object; and a projection optical system that projects an image of a pattern on the first object onto a second object.
The light source produces the illumination light in a substantially single polarization state,
The illumination optical system has a plurality of birefringent members arranged along the traveling direction of the illumination light,
And the direction of the fast axis of at least one birefringent member of the plurality of birefringent members is different from the direction of the fast axis of the other birefringent member,
A projection exposure apparatus, characterized in that, of the illumination light, the specific illumination light with which the first object is irradiated within a specific incident angle range is light in a polarization state whose main component is S-polarized light.   The projection exposure apparatus according to claim 1, further comprising a light flux limiting member that limits the illumination light with which the first object is irradiated to the specific illumination light.   The projection exposure apparatus according to claim 2, wherein the light flux limiting member further limits an incident direction of the illumination light with which the first object is irradiated to a plurality of specific substantially discrete directions. .. A projection exposure apparatus comprising: an illumination optical system that illuminates illumination light from a light source onto a first object; and a projection optical system that projects an image of a pattern on the first object onto a second object.
The light source produces the illumination light in a substantially single polarization state,
The illumination optical system has a plurality of birefringent members arranged along the traveling direction of the illumination light,
And the direction of the fast axis of at least one birefringent member of the plurality of birefringent members is different from the direction of the fast axis of the other birefringent member,
The illumination that passes through at least a part of a specific ring zone area that is a predetermined ring zone area centered on the optical axis of the illumination optical system in a pupil plane in the illumination optical system or in the vicinity thereof. The projection exposure apparatus is characterized in that the light is in a polarization state whose main component is linearly polarized light whose polarization direction is the circumferential direction of the specific ring zone region.   The projection exposure apparatus according to claim 4, further comprising a light flux limiting member that limits the illumination light applied to the first object to a light flux substantially distributed in the specific ring zone region.   The projection exposure apparatus according to claim 5, wherein the light flux limiting member further limits the light flux to a plurality of substantially discrete regions within the specific ring zone region.   7. The projection exposure apparatus according to claim 2, wherein the light flux limiting member includes a diffractive optical element arranged between the light source and the plurality of birefringent members.   At least one member of the plurality of birefringent members has a phase difference between polarizations which is a phase difference given between a linearly polarized light component parallel to the fast axis and a linearly polarized light component parallel to the slow axis of the transmitted light. 7. The projection exposure apparatus according to claim 1, wherein is a non-uniform wave plate that changes non-linearly with respect to the position of the member.   The non-uniform wavelength plate gives a phase difference between polarizations having a two-fold rotational symmetry about the optical axis of the illumination optical system to the specific illumination light or the illumination light distributed in the specific ring zone region. 9. The projection exposure apparatus according to claim 8, comprising one non-uniform wave plate.   The non-uniform wave plate gives a phase difference between polarizations having one-time rotational symmetry about the optical axis of the illumination optical system to the specific illumination light or the illumination light distributed in the specific ring zone region. The projection exposure apparatus according to claim 9, further comprising two non-uniform wave plates.   11. The first and second non-uniform wave plates are characterized in that the directions of the fast axes are shifted from each other by 45° about the optical axis of the illumination optical system as a rotation center. The projection exposure apparatus according to.   7. The projection exposure apparatus according to claim 1, further comprising an optical integrator arranged between the plurality of birefringent members and the first object.   13. The projection exposure apparatus according to claim 12, further comprising a zoom optical system arranged between the plurality of birefringent members and the optical integrator, a variable conical prism group, or a polyhedral prism group.   The projection exposure apparatus according to claim 12 or 13, wherein the optical integrator is a fly-eye lens.   7. A polarization control mechanism arranged between the light source and the plurality of birefringent members, for converting a polarization state of the illumination light from the light source, according to any one of claims 1 to 6. The projection exposure apparatus described.   7. The projection according to claim 1, further comprising a rotation mechanism that allows some or all of the plurality of birefringent members to rotate about an optical axis of the illumination optical system. Exposure equipment.   2. A plurality of sets of the plurality of birefringent members, and a birefringent member exchange mechanism for arranging the plurality of sets of the plurality of birefringent members exchangeably in the illumination optical system. 6. The projection exposure apparatus according to any one of 6.   An exposure method comprising exposing the photoconductor as the second object with an image of a pattern of a mask as the first object, using the projection exposure apparatus according to claim 1. .. A device manufacturing method including a lithography step, comprising:
19. A device manufacturing method, wherein a pattern is transferred to a photoconductor using the exposure method according to claim 18 in the lithography step.   An exposure method, wherein the projection exposure apparatus according to claim 7 is used to expose a photoconductor as the second object with an image of a pattern of a mask as the first object. A device manufacturing method including a lithography step, comprising:
21. A device manufacturing method, wherein a pattern is transferred to a photoconductor using the exposure method according to claim 20 in the lithography process. A projection exposure apparatus comprising: an illumination optical system that illuminates illumination light from a light source onto a first object; and a projection optical system that projects an image of a pattern on the first object onto a second object.
The light source produces the illumination light in a substantially single polarization state,
The projection exposure apparatus, wherein the illumination optical system includes a diffractive optical element and a birefringent member, which are sequentially arranged along a traveling direction of the illumination light. The diffractive optical element substantially limits the illumination light with which the first object is irradiated to specific illumination light with which the first object is irradiated in a specific incident angle range, and
23. The projection exposure apparatus according to claim 22, wherein the birefringent member uses the specific illumination light as light having a polarization state whose main component is S-polarized light.   24. The projection exposure apparatus according to claim 23, wherein the diffractive optical element further limits an incident direction of the illumination light with which the first object is irradiated to a plurality of specific substantially discrete directions. .. The diffractive optical element divides the illumination light into a luminous flux that is distributed in a specific annular zone area, which is a predetermined annular zone area around the optical axis of the illumination optical system, in the pupil plane of the illumination optical system. Practically limiting,
23. The projection exposure apparatus according to claim 22, wherein the birefringent member sets the light flux in a polarization state whose main component is linearly polarized light having a circumferential direction as a deflection direction.   26. The projection exposure apparatus according to claim 25, wherein the diffractive optical element further limits the light flux to a plurality of substantially discrete regions within the specific ring zone region.   27. An exposure method, wherein the projection exposure apparatus according to any one of claims 22 to 26 is used to expose a photoconductor as the second object with an image of a pattern of a mask as the first object. .. A device manufacturing method including a lithography step, comprising:
28. A device manufacturing method, wherein a pattern is transferred to a photoconductor using the exposure method according to claim 27 in the lithography process. An illumination optical device for illuminating the first object with illumination light from a light source,
A plurality of birefringent members arranged along the traveling direction of the illumination light,
And the direction of the fast axis of at least one birefringent member of the plurality of birefringent members is different from the direction of the fast axis of the other birefringent member,
Of the illumination light having a substantially single polarization state that is supplied from the light source, the specific illumination light that is emitted to the first object in a specific incident angle range is converted into a polarization state having S polarization as a main component. An illuminating optical device characterized by using light.   30. The illumination optical apparatus according to claim 29, further comprising a light flux limiting member that limits the illumination light with which the first object is irradiated to the specific illumination light.   31. The illumination optical device according to claim 30, wherein the light flux limiting member further limits an incident direction of the illumination light with which the first object is irradiated to a plurality of specific substantially discrete directions. ..   The illumination optical device according to claim 30 or 31, wherein the light flux limiting member includes a diffractive optical element.   At least one member of the plurality of birefringent members has a phase difference between polarizations which is a phase difference given between a linearly polarized light component parallel to the fast axis and a linearly polarized light component parallel to the slow axis of the transmitted light. Is an inhomogeneous wave plate that changes non-linearly with respect to the position of the member.   The non-uniform wavelength plate gives a phase difference between polarizations having a two-fold rotational symmetry about the optical axis of the illumination optical system to the specific illumination light or the illumination light distributed in the specific ring zone region. 34. The illumination optical device according to claim 33, comprising one non-uniform wave plate.   The non-uniform wave plate gives a phase difference between polarizations having one-time rotational symmetry about the optical axis of the illumination optical system to the specific illumination light or the illumination light distributed in the specific ring zone region. The illumination optical apparatus according to claim 34, further comprising two non-uniform wave plates.   36. The first and second non-uniform wavelength plates are characterized in that the directions of the fast axes are shifted from each other by 45° about the optical axis of the illumination optical system as a rotation center. The illumination optical device according to.   32. The illumination optical device according to claim 29, further comprising an optical integrator arranged between the plurality of birefringent members and the first object. The light flux limiting member is a diffractive optical element,
32. The illumination optical apparatus according to claim 30, further comprising an optical integrator arranged between the plurality of birefringent members and the first object. An illumination optical device for illuminating the first object with illumination light from a light source,
An illumination optical device comprising: a diffractive optical element and a birefringent member, which are sequentially arranged along a traveling direction of the illumination light. The diffractive optical element substantially limits the illumination light with which the first object is irradiated to specific illumination light with which the first object is irradiated in a specific incident angle range, and
40. The illumination optical device according to claim 39, wherein the birefringent member sets the specific illumination light to light in a polarization state having S-polarized light as a main component.   The illumination optical device according to claim 40, wherein the diffractive optical element further limits an incident direction of the illumination light with which the first object is irradiated to a plurality of specific substantially discrete directions. .   42. The illumination optical device according to claim 39, further comprising an optical integrator arranged between the birefringent member and the first object.

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